From today 4/6/'13 there's an onward rail service to Wexford/Wicklow/Dublin meeting the afternoon sailing from Fishguard at Rosslare Harbour. A through ticket can be purchased to include rail travel from any National Rail station in Wales/England/Scotland to Rosslare Harbour.
A delightful journey especially in summer.
The ferry terminal and rail station are combined at Fishguard Harbour making for a hassle free relaxed experience. To plan/view times: